SARS-CoV-2 Seroprevalence and Neutralizing Antibody Response after the First and Second COVID-19 Pandemic Wave in Croatia

Vilibić-Čavlek, Tatjana; Stevanović, Vladimir; Ilić, Maja; Barbić, Ljubo; Capak, Krunoslav; Tabain, Irena; Krleža, Jasna Leniček; Ferenc, Thomas; Hruškar, Željka; Topić, Renata Zrinski; Kaliterna, Vanja; Antolović-Požgain, Arlen; Kučinar, Jasmina; Koscak, Iva; Mayer, Davor; Sviben, Mario; Antolašić, Ljiljana; Milašinčić, Ljiljana; Bucić, Lovro; Ferenčak, Ivana; Kaić, Bernard

doi:10.3390/pathogens10060774

Cited by 20 publications

(23 citation statements)

References 36 publications

(44 reference statements)

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“…Similar to the results of other studies, our study showed that symptomatic patients developed higher NT antibody titers compared to asymptomatic ones. Compared to a previous Croatian study in the general population, the prevalence of NT antibodies was slightly higher in the SOTRs (3.1% vs. 2.2%) ( 6 ). However, it is important to note that NT antibodies were detected in 15.6% ELISA positive SOTRs compared to 8.3% of the general population.…”

Section: Discussioncontrasting

confidence: 80%

Section: Discussionmentioning

confidence: 99%

“…Besides, 2.7% of healthcare workers tested seropositive using ELISA, while NT antibodies were found in only 1.5% of the tested ( 4 ). Additionally, 2.2% of the general population were shown to be ELISA positive after the first wave, with low titers of NT antibodies detected in only 0.2% of individuals ( 6 ). A more recent study conducted among children from Children’s hospital Zagreb showed that the prevalence of anti-SARS-CoV-2 antibodies differed significantly between the first wave (2.9%) and the second wave (8.4%) of the COVID-19 pandemic ( 7 ).…”

Section: Discussionmentioning

confidence: 99%

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Seroprevalence of SARS-CoV-2 in Croatian solid-organ transplant recipients

Mrzljak¹,

Jureković²,

Pavičić-Šarić³

et al. 2021

Biochem. med. (Online)

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Introduction The data on the coronavirus disease (COVID-19) in solid-organ transplant recipients (SOTRs) in Croatia is unknown. The aim of this study was to analyze the seroprevalence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in Croatian SOTRs. Materials and methods From 7 September to 27 November 2020 (beginning of the second COVID-19 pandemic wave), a cross-sectional screening for COVID-19 was performed in the adult outpatient liver (LTRs; N = 280) and kidney transplant recipients (KTRs; N = 232). Serum samples were initially tested for SARS-CoV-2 IgG antibodies using a commercial enzyme-linked immunosorbent assay (ELISA; Vircell Microbiologists, Granada, Spain). All positive samples were confirmed using a virus neutralization test (VNT). Data on risk exposure and COVID-19 related symptoms were collected using a questionnaire. Results The transplanted cohort’s seroprevalence detected by ELISA and VNT was 20.1% and 3.1%, respectively. Neutralizing (NT) antibodies developed in 15.6% of anti-SARS-CoV-2 ELISA IgG positive SOTRs. The difference in seropositivity rates between LTRs and KTRs was not statistically significant (ELISA 21.1% vs . 19.0%, P = 0.554; VNT 3.6% vs . 2.6%, P = 0.082). Overall VNT positivity rates were higher in patients who reported participation in large community events (5.9% vs . 1.0%; P = 0.027) as well as in patients who reported COVID-19 related symptoms in the past six months. In addition, symptomatic VNT positive patients showed significantly higher (P = 0.031) NT antibody titers (median 128, interquartile range (IQR) = 32-128) compared to asymptomatic patients (median 16, IQR = 16-48). Conclusions This study showed that 15.6% of anti-SARS-CoV-2 ELISA positive Croatian SOTRs developed NT antibodies indicating protective immunity. Further studies are needed to determine the dynamic of NT antibodies and COVID-19 immunity duration in immunocompromised populations such as LTRs and KTRs.

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Section: Discussioncontrasting

confidence: 80%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Seroprevalence of SARS-CoV-2 in Croatian solid-organ transplant recipients

Mrzljak¹,

Jureković²,

Pavičić-Šarić³

et al. 2021

Biochem. med. (Online)

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“…The difference in serological reactivity is further confirmed by comparing serological testing results between dogs and human samples. In December 2020, 458 human serum samples were collected in Zagreb as a part of the general population serosurvey [22]. Serological tests were done by the same research group as in this study, using the same methods in the same laboratory settings.…”

Section: Discussionmentioning

confidence: 99%

The Emergence of SARS-CoV-2 within the Dog Population in Croatia: Host Factors and Clinical Outcome

Stevanović

Tabain

Vilibić-Čavlek

et al. 2021

Viruses

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Over a year into the COVID-19 pandemic, there is growing evidence that SARS-CoV-2 infections among dogs are more common than previously thought. In this study, the prevalence of SARS-CoV-2 antibodies was investigated in two dog populations. The first group was comprised of 1069 dogs admitted to the Veterinary Teaching Hospital for any given reason. The second group included dogs that shared households with confirmed COVID-19 cases in humans. This study group numbered 78 dogs. In COVID-19 infected households, 43.9% tested ELISA positive, and neutralising antibodies were detected in 25.64% of dogs. Those data are comparable with the secondary attack rate in the human population. With 14.69% of dogs in the general population testing ELISA positive, there was a surge of SARS-CoV-2 infections within the dog population amid the second wave of the pandemic. Noticeably seroprevalence of SARS-CoV-2 in the dog and the human population did not differ at the end of the study period. Male sex, breed and age were identified as significant risk factors. This study gives strong evidence that while acute dog infections are mostly asymptomatic, they can pose a significant risk to dog health. Due to the retrospective nature of this study, samples for viral isolation and PCR were unavailable. Still, seropositive dogs had a 1.97 times greater risk for developing central nervous symptoms.

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“…Neutralizing antibody titer was defined as the reciprocal of the highest serum dilution that showed at least 50% neutralization. Neutralizing antibody titer <8 was considered negative and that of ≥8 was considered positive ( 9 ). Only VNT results are presented.…”

Section: Methodsmentioning

confidence: 99%

Waning immunity six months after BioNTech/Pfizer COVID-19 vaccination among nursing home residents in Zagreb, Croatia

et al. 2021

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Aim To assess the humoral immunity to COVID-19 in nursing home residents six months after vaccination. Methods This seroepidemiological research enrolled 118 residents of one nursing home in Zagreb. All participants received two doses of BioNTech/Pfizer COVID-19 and had no previously detected SARS-CoV-2 infection. The samples were tested for the presence of neutralizing antibodies using a virus neutralization test. A SARS-CoV-2 strain isolated in Vero E6 cells from a Croatian COVID-19 patient was used as a stock virus. Neutralizing antibody titer was defined as the reciprocal of the highest serum dilution that showed at least 50% neutralization. Neutralizing antibody titer ≥8 was considered positive. Results Sixty-four (54%) participants had a positive neutralizing antibody titer, 27 (23%) had a low positive titer (titer 8), and 27 (23%) had a negative titer. Women had a significantly higher median titer than men (16 [interquartile range, IQR 24] vs 8 [IQR 12], Mann-Whitney U = 1033, P = 0.003). Age was negatively but not significantly correlated with neutralizing antibody titer (Spearman’s rho -0.132, P = 0.155). Conclusion Almost half of the participants (46%) had a negative or low positive titer six months after having been fully vaccinated. This study suggests that humoral immunity among nursing home residents considerably wanes six months after BioNTech/Pfizer COVID-19 vaccination. Our results could contribute to the discussion about the need for a booster dose.

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SARS-CoV-2 Seroprevalence and Neutralizing Antibody Response after the First and Second COVID-19 Pandemic Wave in Croatia

Cited by 20 publications

References 36 publications

Seroprevalence of SARS-CoV-2 in Croatian solid-organ transplant recipients

Seroprevalence of SARS-CoV-2 in Croatian solid-organ transplant recipients

The Emergence of SARS-CoV-2 within the Dog Population in Croatia: Host Factors and Clinical Outcome

Waning immunity six months after BioNTech/Pfizer COVID-19 vaccination among nursing home residents in Zagreb, Croatia

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